The overall goal of this project is to obtain structural information on theknown and presumptive neurosecretory proteins of several of the identified neurons of the abdominal ganglion of Aplysia. We have developed a method for obtaining peptide maps of these proteins and intend to apply it to the study of members of the proteolytic processing sequences which generate characteristic peptides in these neurons. We will investiate the structural transformations accompanying processing of the peptide egg-laying hormone of the bag cells and compare these to similar steps inthe other neurons. Since there are demonstrable differences between the products of the various cell types, such a comparison should allow us to distinguish between steps which are common to each of these cells, and thus may be comparable to those involved in the production of vertebrate secretory proteins, and those which differ between cells, and thus may be responsible for the generation of unique, cell-specific products. We also intend to see if some of these cell types are generating different products from similar precursors, and if so, how this is accomplished. We expect to obtain information concerning themetabolism of secretory proteins in general and on the mechanisms responsible for functional specificity in neurosecretory cells.